Fix Error Prone errors

Soong wasn't including android_app or android_test sources in the
javac-check target used for the Error Prone build, which allowed
some Error Prone errors to get in.  Fix them so Error Prone can be
re-enabled for these targets.

Fixes:
packages/modules/NetworkStack/tests/integration/src/android/net/ip/IpClientIntegrationTest.java:1182: error: [JUnit4TestNotRun] This looks like a test method but is not run; please add @Test and @Ignore, or, if this is a helper method, reduce its visibility.
packages/modules/NetworkStack/tests/unit/src/android/net/ip/IpClientTest.java:352: error: [JUnit4TestNotRun] This looks like a test method but is not run; please add @Test and @Ignore, or, if this is a helper method, reduce its visibility.
packages/modules/NetworkStack/tests/unit/src/com/android/server/connectivity/ipmemorystore/IpMemoryStoreServiceTest.java:772: error: [JUnit4TestNotRun] This looks like a test method but is not run; please add @Test and @Ignore, or, if this is a helper method, reduce its visibility.

Bug: 146455923
Test: m RUN_ERROR_PRONE=true javac-check
Change-Id: Iec6c4d9e4cde39f98068b3351a1d828e45abf54b